A12-week experiment was conducted to evaluate the influences of thiamine ongrowth performance, and intestinal mitochondrial biogenesis and function of Megalobramaamblycephala fed a high-carbohydrate (HC) diet. Fish (24·73 (sem 0·45) g) were randomly assigned to one of four diets: two carbohydrate (CHO) levels (30 and 45 %) and two thiamine levels (0 and 1·5 mg/kg). HC diets significantly decreased DGC, GRMBW, FIMBW, intestinal activities of amylase, lipase, Na+, K+-ATPase, CK, complexes I, III and IV, intestinal ML, number of mitochondrial per field, ΔΨm, the P-AMPK: T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, mitochondrial transcription factor A, Opa-1, ND-1 and COX-1 and 2, while the opposite was true for ATP, AMP and reactive oxygen species, and the transcriptions of dynamin-related protein-1, fission-1 and mitochondrial fission factor. Dietarythiamine concentrations significantly increased DGC, GRMBW, intestinal activities of amylase, Na+, K+-ATPase, CK, complexes I and IV, intestinal ML, number of mitochondrial per field, ΔΨm, the P-AMPK:T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, Opa-1, ND-1, COX-1 and 2, SGLT-1 and GLUT-2. Furthermore, a significant interaction between dietary CHO and thiamine was observed in DGC, GRMBW, intestinal activities of amylase, CK, complexes I and IV, ΔΨm, the AMP:ATP ratio, the P-AMPK:T-AMPK ratio, PGC-1β protein expression as well as the transcriptions of AMPKα1, AMPKα2, PGC-1β, Opa-1, COX-1 and 2, SGLT-1 and GLUT-2. Overall, thiamine supplementation improved growth performance, and intestinal mitochondrial biogenesis and function of M. amblycephala fed HC diets.

The population dynamics of Sphaerospora dicentrarchi and S. testicularis, myxosporean parasites of sea bass (Dicentrarchus labrax), was studied in different groups of cultured and wild fish. S. dicentrarchi prevalence was higher for wild fish (100%) than for cultured ones (70.5%). Infection levels increased with host age and there were no significant sex differences in cultured fish. Among parasitized organs, the gall bladder and intestine registered the highest infection levels in wild and cultured fish. A progressive increase in infection levels of S. testicularis was observed in cultured males during the spawning season in four consecutive periods. The evolution of the percentage of the different parasitic stages is pointed out. The infection seems to be related to water temperature and gonadal maturation.

Fish meal is the most widely used protein source in commercial eel foods and information on the nutritive value of more economical protein sources is needed in order to improve cost-effectiveness of diets. This investigation was conducted to determine apparent digestibility coefficients of available plant and animal meals for juvenile Australian short-finned eel (Anguilla australis australis, Richardson). The suitability of a modified Guelph-type settlement faecal collector in eel digestibility studies was assessed. Animal by-product (spray-dried meat solubles; blood meal; high fat poultry meal) and plant protein (soya bean; canola; maize gluten; lupin; field pea) meals were mixed with a reference diet and marker (0·3: 0·69: 0·01) and the resultant test diets given to the juvenile eels (3·15 (s.e. 0·42) g) at 0·05 live weight per day. The reference diet and all the test diets were well accepted by the fish. Apparent digestibility coefficients for crude protein (ADCCP) for maize gluten meal (MGM), lupin meal (LM) and blood meal (BM) were found to be 0·97, 0·96 and 0·96 respectively and they were significantly (P < 0·001) higher than that for the other ingredients. However, apparent digestibilities for dry matter (ADCDM) and energy (ADCkJ) were significantly (P < 0·0001) higher for animal by-products than for plant proteins except for maize gluten meal. This was explained by the higher content of nitrogen free extractives in the former plant proteins. There was a strong positive correlation between ADCDM and ADCkJ for all ingredients (P < 0·01). Weaker positive correlations were also found between ADCCP and ADCDM and between ADCCP and ADCkJ. Similar results obtained for warm water species using similar faecal collection techniques and over limited eel digestibility data support the suitability of the modified Guelph-type settlement collector system in digestibility studies with juvenile eels.

Construction of small water-harvesting structures (WHS) across seasonal streams, in the vicinity of cultivated areas, has proved to be a viable technique of water harvesting in the Shiwalik foothills of northern India. This paper reports on the performance and impact of one such structure in this area. Sufficient rainwater was available for harvesting because 86 ± 5.4% of monsoon rainstorms were runoff producing, resulting in collection of 29 ± 5% of the total monsoon rainfall. Out of this harvested water around 62% was available for irrigation at the start of the Rabi season (i.e., the dry season starting around 1 November). With time the water losses from the WHS declined from 66% in the first year of construction (1985) to 18% in 1996, because of sealing of soil pores from siltation of the reservoir bed. The life of the WHS was estimated to be 65 years at the observed average siltation rate of 47 Mg/ha/year. After construction of the WHS, the area under cultivation increased from 17 ha to 20 ha and the cropping intensity by 170 to 200%. The Rabi crop yields were approximately doubled. Assured availability of water and fodder increased milk production by 103%. Additional annual income of Rs. 7,015 per year was generated through fish culture. A rise in the groundwater level and higher growth of vegetation around the WHS were also observed. On the basis of increased crop production alone, the WHS proved to be an economically viable venture resulting in a benefit:cost ratio of greater than one. Socioeconomic considerations in the management of the WHS were also studied and showed that community involvement was essential to the success of this project.

The present work examines the usefulness of the combination of multivariate analyses and further one-way analysis of variance in the search for links between causes and effects in heterologous stimulation of spawning in fish. Stimulations with both 20 and 50 μg.kg–1 doses of [D Trp6] luteinizing hormone-releasing hormone analogue (LH-RHa) were effective in inducing and synchronizing spawning of red drum, Sciaenops ocellatus. Oocyte development monitoring using ovarian biopsy allowed treatment injections at different stages of maturation. The influence at stimulation time of female oocyte development state upon further development was shown. An interesting potential of second stimulation, leading to high quality spawns, was established and factors of success were identified. The best conditions for stimulation success were simultaneously late stage of oocyte development characterized by the beginning of oil droplet coalescence, high ovarian homogeneity quoted by the proportion of most developed oocytes in the biopsy sample, and low dose of hormone (20 μg.kg–1) for both first and second stimulations.

The relationship between serum protein, immunoglobulin concentrations and protein molecular weight profile (PMWP) alterations of sea bass (131.3 ± 4.3 g) reared in sea water with sublethal concentrations of ammonia was studied over two periods totalling 116 days. During the exposure period (62 days) the first group (group 1) lived in sea water with 0.204 mg·L−1 unionized ammonia nitrogen equivalent to 12 % of the lethal concentration for 50 % of a population exposed for 96 h to ammonia (96-h LC50), whilst the second group (group 2) lived in sea water with 0.340 mg·L−1 UIA-N equivalent to 20 % of the 96-h LC50 of ammonia. Then, the two groups were left for a recovery period (54 days) in the same water as the control group (group 0). The determination of the total immunoglobulin (Ig) concentration was carried out by enzyme-linked immunosorbant assay (ELISA). Gel filtration columns were used for the serum PMWP. Serum Ig concentration of the exposed fish (group 2: 1.76 ± 0.43 mg·mL−1; group 1: 1.19 ± 0.33 mg·mL−1) was lower than the control group 13.39 ± 1.01 mg·mL−1) after 21 days of exposure period but this difference was reduced at the end of this period (day 62) and treated group Ig concentrations switched to higher than the control group after the recovery period (day 116, group 2: 9.75 ± 1.84 mg·mL−1; group 1: 7.50 ± 1.22 mg·mL−1 group 0: 6.38 ± 1.13 mg·mL−1). In fact, at the end of the experiment, the cumulative Ig production difference between fish exposed to ammonia and the control was less than 10%. Although a similar evolution of the Ig serum occurred with protein concentration, the serum protein concentration deficit of group 1 was restored at the end of the exposure period (group 2: 46.49 ± 2.34 mg·mL-1; group 0: 46.74 ± 1.97 mg·mL−1) and the cumulative production during the experiment was not significantly different between group 1 and group 0. However, this remained lower for group 2. During the exposure period, the PMWP of treated fish moved towards smaller molecular weight proteins. This alteration of the PMWP showed that the 0.2-kDa fraction increased, and another fraction appeared at the end of the exposure period. However, at the end of the recovery period, no difference was found between the PMWPs of control and treated fish. The alterations of the serum protein and Ig of fish reared, for a limited period (2 months), in water with sublethal concentrations of ammonia (20 % 96-h LC50 or less) should disappear completely after a few months in normal rearing conditions.

Self-feeding systems allow fish to freely express feeding activity. A simple rod at the water surface can act as a trigger and provide fish with a way of obtaining pellets from a feeder. Such a rod presented to experienced European seabass, Dicentrarchus labrax, may lead to feed wastage, probably as a result of unintentional fish contacts with the trigger. Trigger protection screens have been designed to prevent fish contacting the trigger by chance, and the efficacy of such screens was tested. Nocturnal and diurnal feed delivery and feed wasted were compared under conditions where the rod was unprotected or protected by semi-cylindrical or cylindrical screens. Tests were conducted using an unrestricted self-feeding regime (reward: 0.2 g pellet per kg of body weight and per fish contact) in juvenile seabass (57 g body weight) fed for 28 days at 21.3 °C. Fish were subjected to a 4-h L:20-h D (light:dark) photoperiod. The daily feed demand pattern and the nocturnal and diurnal feed wastage were recorded. Fish activated the trigger predominantly at night, except in the case of one group exposed to a trigger protected by a semi-cylindrical screen. in the latter, triggering activity was progressively distributed throughout the light:dark cycle. The cylindrical screens markedly reduced feed wastage and seabass were able to locate and activate the trigger (even in total darkness) to obtain a reward.

Tous les grands groupes de parasites de poissons, aussi bien Protozoaires que Métazoaires, ont été signalés chez les Siluroidei. D'après leur localisation, chez l'hôte on peut distinguer: les ectoparasites qui vivent sur le tégument et/ou sur les branchies ; les mésoparasites que l'on rencontre surtout dans le système digestif; les endoparasites qui sont dans le corps (cavités ou tissus). Une accumulation anormale de parasites, par rapport à l'équilibre généralement observé dans la nature, engendre des effets pathogènes chez les poissons en aquaculture. Trois facteurs semblent importants dans le déterminisme de cette accumulation: 1) la vitesse de multiplication, liée au mode de reproduction, en particulier asexué; 2) la taille de l'organisme parasite, qui peut faciliter l'envahissement de l'hôte et 3) le type de cycle biologique, direct (monoxène ou holoxène), ou indirect (hétéroxène). La bibliographie consacrée aux Siluroidei montre que les agents pathogènes ou les parasites les plus étudiés dépendent de la forme d'élevage pratiquée (industrielle ou artisanale). Les parasitoses les plus couramment citées pour leur importance chez Ictalurus punctatus sont détaillées. La question du parasitisme des autres Siluroidei élevés ou potentiellement intéressants est posée.

Specificities of the structural, chemical, physical and sensory characteristics of the flesh are reviewed and related to different aspects of flesh quality. Potential for processing of catfish is high in terms of mechanization but rather low in terms of processing yields. The variability observed in body conformation traits supports the possibility to improve processing yields by genetic selection. Little is known on the structure of catfish flesh but a higher cohesiveness due both to greater connective tissue strength and probably a greater homogeneity of muscle tissues is observed, compared to other freshwater species. Although the presence of adipose tissues has not been demonstrated, intermuscular adipose tissues contributes with red muscle to lipid deposits in commercial size. Lipid content in catfish flesh increases with age but even at commercial size it is still lower than what is reported in other cultured fish. There is however a tendency in recent years for an increase in lipid content in catfish flesh due to increasedlipid content in the diet. Thus, further information on the control of lipid deposits is required in future especially in a view to improve taste and processing yields. The lipid composition of neutral lipids reflects that of the diet with high levels of monounsaturated fatty acids and a low w3/w6 ratio.Flesh colour is very subtle but it could be controlled either by the use of pigment supplementation in the diet or by rearing non pigmented catfish. Other physical characteristics of the flesh are very stable during the cooking process. Cooked flesh has a relatively low water-holding capacity and a low resistance to mechanical stress (compression, extrusion) thus contributing to the juiciness and tenderness of the flesh. The sensory characteristics of the flesh are somewhat neutral but consumers are able to detect thespecific characteristics of different species such as Channel catfish, African catfish and European catfish. Significant efforts to standardize the sensory evaluation of Channel catfish have been made in the USA but flavor and aroma of catfish seem to be more related to the fish itself than to other factors such as the diet composition. New data is available on off-flavors related to geosmin and methyl-iso-borneol. Specific control of the phytoplankton species which produce these compounds appears to be possible.Storage on ice affects the flesh acceptability as it does for other fish species, but catfish flesh seems to be stable at least physically during freezing. Traditional processing is used for preservation of the flesh. New processing methods have been tested for the diversification of catfish products or to produce substitutes for other animal products. Catfishes are generally shown to be suitable for processing.

Large numbers of female broodstock (Clarias macrocephalus) are required cach year to produce hybrid catfish which retain the materna1 meat quality of Thai walking catfish and the paternal fast growing and disease resistant traits of the African catfish (C1arias gariepinus). Therefore, diploid meiotic gynogens were induced in Thai walking catfish and their potential use for aquaculture was evaluated. Induction was performed using UV-irradiated sperm of stripped catfish (Pangasius sutchi) followed by either cold or heat shock at 4.5 min after activation. Heat shock at 42 °C for 1 min was the best among various heat shock regimes. Cold shock (7 °C for 14 min) gave significantly higher percentages of meiotic diploid fry (26-41%) than the heat shock (12-26%). Six-month-old meiotic gynogens were all female and showed slightly inferior growth to male and femalc controls. The six-month-old control-males and females and the gynogens were not different in size. Survival of the gynogens (73 ± 8 %) was slightly inferior to the mixed sex control (87 ± 10 %). Gonado-somatic index of gynogens at 1 year of age (5.7%) was slightly inferior to that of the control female (8.8 9%). Therefore, the direct use of all female meiotic gynogens to enhance production of Thai walking catfish, may be doubtful. However, their use for breeding purposes is promising providing that inbreeding depression is eliminated.

L'association d'un prédateur à l'élevage de tilapias pour en contrôler la reproduction indésirable est aujourd'hui effectuée par un nombre croissant de pisciculteurs africains. Dans ce cadre, les Siluriformes (Clarias ou Heterobranchus sp.) sont souvent considérés comme ayant une double fonction : prédation et polyculture. Les résultats d'élevage associés Clarias gariepinus-Oreochromis niloticus montrent qu'un nombre important d'individus de Clarias gariepinus est nécessaire au contrôle total de la reproduction des juvéniles d'O. niloticus mis en charge et qu'ils exercent une compétition vis-à-vis des ressources alimentaires disponibles (aliment et/ou engrais) dans l'étang. Pour contrôler une population de 1 200 tilapias (mâles et femelles) en étang de 10 ares, une population de 260 Clarias gariepinus de poids moyen initial supérieur à 150 g est nécessaire et la croissance des tilapias est inférieure à celle d'un élevage identique dans lequel C. gariepinus est remplacé par un prédateur strict (Hemichromis fusciatus). Ces résultats, confirmés avec un autre Siluriforme, Heterobranchus isopterus, conduisent à privilégier dans le Centre Ouest de la Côte d'Ivoire la pratique d'une polyculture basée sur 3 espèces: O. niloticus, un prédateur strict (Hemichromis fasciatus ou Parachanna obscura) et un siluriforme, Heterohranchus isopterus dont la vocation n'est pas de contrôler la reproduction des tilapias mais de contribuer quantitativement et qualitativement à la production finale. H. longifilis, quant à lui, présente un taux de croissance trop élevé pour ce type d'association, entraînant rapidement un écart de taille avec les tilapias mis en charge sur lesquels il exerce une prédation de même que sur les carnassiers stricts sans contrôler efficacement la prolifération d'alevins de tilapias. Les rendements en H. isoprerus (0,l individu.m−2) peuvent atteindre 1 t.ha−1.an−1 et un poids moyen de 500 g après un cycle de 6 mois d'élevage. Sur la base de ces résultats, obtenus en vraie grandeur, cette logique de polyculture s'est déjà imposée auprès de nombreux pisciculteurs ivoiriens et semble pouvoir constituer un système d'élevage à vulgariser pour l'avenir.